The goal of this study is to characterize the human neutrophil dopaminergic receptor. The neutrophil is a unique model for a peripheral dopamine receptor since it is a human cell which can be purified and studied in-vitro. The proposed investigation will explore the pharmacologic specificity, affinity and number, and mechanism of action of the dopamine receptor. Neutrophils will be purified from blood collected from normal volunteers: The assay for intact cell function and drug effect will be the stimulated release of lysosomal enzymes from neutrophils. Intact cell data for the adrenergic and dopaminergic compounds will then be compared to data obtained from direct binding of tritium labeled ligands to a purified membrane preparation. The use of both an intact cell assay and a direct binding assay should allow one to estimate the physiological significance of affinity data for the various dopaminergic compounds. This information may be useful in evaluating therapeutic agents which may act via a dopaminergic receptor. Furthermore, the mechanism of dopamine receptor mediated modulation of cell function will be explored by determining the effects of receptor stimulation on cellular calcium fluxes. This data should enhance the understanding of the hormone-receptor interaction and the mechanism of altering cellular function.